In recent years metallic lithium or lithium compounds such as lithium salts, have been used in various fields. Their application typically includes lithium batteries, lithium-containing ceramic materials, coolant adsorbents, pharmaceuticals, aluminum alloying materials, and nuclear fusion fuel materials, and the like. The metallic lithium or lithium compounds have been obtained from Li-containing ore, such as spodumene, amblygonite, petalite, and lepidolite; brine; or geothermal water. For example, the lithium is extracted from these raw materials, in the form of a lithium salt, by adsorption using an adsorbent (e.g., aluminum hydroxide) or electrolysis using an ion-exchange membrane made of resin. Having found a use as a power source of small-sized appliances, such as watches, cameras, calculators, and IC cards, lithium batteries have been enjoying a drastically increasing demand, and used lithium batteries have been increasing concomitantly. Accordingly, attention has been paid to the reuse or recycle of the lithium component from the used lithium batteries.
Of the above-mentioned extraction methods, the adsorption method hardly produces high purity lithium salts due Lo the low extraction efficiency so that a step of purification is needed. Therefore, this method may be disadvantageous from the standpoint of labor and cost. On the other hand, the electrolysis method is a technique in which lithium (Li) ions are electrically moved through an ion-exchange membrane made of resin. The efficiency by the electrolysis method is not satisfactory because not only Li ions but hydrogen ions pass through the ion-exchange membrane